I think you need to brake harder, and either be on the brake or the throttle. You seem to be coasting before the corners and that is just waste of time, and that also means that you braked too early or slowed too much, in this case not enough sometimes.
I guess the old slow in - fast out is a good advise. Try to figure out how fast you can accelerate from the corners and hit the apex and then find out how late can you brake down to that speed maintaining a good line.
Now to test drive your set and see how is it.
edit. Well, Kev was on it earlier and more detail.